1. Field of the Invention
The present invention relates generally to a semiconductor sense amplifier and more specifically to an address buffer of flip-flop type for a dynamic RAM, which can convert a TTL (Transistor Transistor Logic) level address input signal to MOS (Metal Oxide Silicon) logic level complementary address signals.
2. Description of the Prior Art
MOS memories are suitable for storing a great number of data. In particular, MOS-type dynamic RAMs have widely been used as the main memory for a computer, because current consumption is extremely small when not activated. In the MOS DRAMs, a sense amplifier is used as a first-stage input circuit. Further, in order to satisfy high speed operation and low power consumption, address buffers of dynamic flip-flop type have widely been used as the sense amplifier. This address better serves to convert a bipolar logic level (TTL) signal to complementary MOS logic level signals. The TTL input signal level can be sensed by the address buffer on the basis of a difference in conductance between an address input FET(Field Effect Transistor) to which a TTL level signal is applied and a reference input FET to which a reference signal (mean TTL level) is applied.
In the prior-art address buffer circuit of sense amplifier, however, since the above two, address input and reference input, FETs are turned on to a TTL level (-1 to 6.5 V, in more detail "L" is -1.0 to 0.8 V and "H" is 2.4 to 6.5 V) different from the MOS level (0 to 5 V), current flows through these FETs, thus increasing power consumption and substrate current. Further, what is worse, an increase in substrate current inevitably causes fluctuations of FET threshold level and deterioration in conductance of the FETs, thus resulting in reduction of sensitivity and long-term reliability of the address buffer circuit.
The circuit configuration of the prior-art address buffer circuit will be described in greater detail hereinafter with reference to the attached drawings under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.